At present, the cancers are treated mainly through surgery, chemotherapy, and radiotherapy, but all of which suffer from drawbacks. In clinic, the tumor cells cannot be completely removed by surgical operations in most cases, thus leading to potential reoccurrence of tumors in the patients. Moreover, the chemo- and radiotherapy generally cause extremely serious side effects to normal tissues. Therefore, photothermal therapy gradually becomes prevalent.
Photothermal therapy is a technique in which a photothermal therapeutic material in a subject is irradiated by IR light at a wavelength that strongly penetrates the tissues of the subject, such that the light energy is absorbed by the material and converted into heat energy, whereby the cancer cells are killed by utilizing the heat energy. Moreover, due to the focusing characteristics of the light, the damage to normal tissues peripheral to the cancer or tumor tissues can be effectively reduced, thereby decreasing the side effects.
Besides, cocktail therapy is frequently used in clinic in the treatment of tumors, and multiple therapies are used to improve the cancer treatment effect. For instance, the photothermal therapy is used in combination with the chemo- or radiotherapy to achieve a dual therapeutic efficacy and significantly reduce the occurrence of drug resistance of tumor cells in a subject.
Currently, when the photothermal therapy is used in combination with the chemotherapy, the photothermal therapy may be effected by using various morphologies of nano-gold, for example, gold nanorods, gold nanoshells, and gold nanoboxes, and the chemotherapy may be effected by using common anti-cancer agents, for example, paclitaxel, camptothecin, and anthracycline. The two ingredients are combined with each other, to form a photothermal chemotherapeutic carrier. However, in practical use, some important issues exist. Because a majority of chemotherapeutic agents are lipid soluble and cannot be administered to animals by intravenous injection, they must be orally taken or carried by means of entrapment. Moreover, the release from the photothermal therapeutic pharmaceutical carrier is also limited. During intravenous injection, due to the existence of concentration gradient, the chemotherapeutic agent is naturally released from many pharmaceutical carriers in the prior art before reaching to the tumors. As a result, unwanted side effects are caused, the drug concentration arrived at the tumors is reduced, and controlled release of the drug cannot be achieved. Furthermore, surface modification of the nano-gold is complex and time-consuming. Although nano-gold has a high photothermal effect, the synthesized nano-gold has the disadvantages of high toxicity and low biological compatibility, and should undergo surface modification before use in a subject.
In view of this, there is an urgent need in the art for an improved thermosensitive pharmaceutical carrier, to overcome the disadvantages in the prior art.